As we go through life, we gain different kinds of knowledge. Sometimes this knowledge affects only a small part of our understanding of reality. When someone tells me that she ate pizza last night, such knowledge, ceteris paribus, does not effect any significant changes in my worldview. Some knowledge, the “knowing-how” kind of knowledge (what I call “skill”) is likewise worldview-ambivalent, in that after gaining such knowledge, our interpretation of events (our perception of their “meaning”) remains basically the same, except perhaps in a specific area. For example, learning how to use a computer program might allow me to understand the purpose behind actions of other people using the same program, but that knowledge does not affect the fundamental ways in which I perceive reality.
On the other hand, there are certain kinds of knowledge, both knowledge-that and knowledge-how (both factual knowledge and skill), that do fundamentally affect how we understand reality. As an example in the first category, take the knowledge that the earth is round. Our thought relationship to such objects as the sun, the moon, and the stars is completely different than that of people a thousand years ago, even though neither the sun, the moon, nor the stars have changed much. Examples in the second category can be found as well (which is what I will mainly be talking about).
So far, I have said nothing surprising. It could all have been stated more succinctly: “Some facts/skills are more important than others.” No doubt anyone would agree. Now I want to make an additional claim: some forms of knowledge are of a sort that, upon gaining, are entrenched so deeply in our mental frameworks that we cannot even coherently imagine seeing the universe in the same way as we did prior to gaining the knowledge. Here is where the skill examples come in. It is easy to imagine, on one hand, a flat earth, even while retaining the knowledge of its roundness. I can form a coherent picture of such an earth in my head. Now take a certain kind of skill–being able to speak and understand English with the facility of a native speaker. Though I know it’s a completely coherent possibility that I see a well-formed English sentence while not understanding it, I can’t actually imagine seeing a well-formed English sentence and not understanding it. Any time I imagine a well-formed English sentence, and look at the words, I cannot help but understand it. That is just what it is to be a competent reader/listener of English!